Oil composition and process of retarding development of rancidity therein



FIFSEFOZL ratentecl Uct. 6, i333 THOMASHUN'ION ROGERS, OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DU PONT DE NEIVIOURS & 00., 0F WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE OIL COMPOSITION AND PROCESS OF RETARDING DEVELOPMENT OF RANGIDITY THEREIN No Drawing. Application filed August 21, 1922, Serial No. 583,865.

This invention relates to compositions at least one constituent of which is an organic material, for instance, a liquid such as an unsaturated fatty oil, which has a tendency to undergo a chemical change at ordinary room temperature (20 C.) when exposed to air and to actinic light; and of which another constituent is oxalic acid, or a salt or ester thereof, functioning to prevent or inhibit said chemical change of the first mentioned constituent. My invention also includes the process of inhibiting the oxidation in the presence of air of an organic material of the kind above-mentioned by dispersing, at least throughout the surface portion of said material, oxalic acid, or a salt, ester or other active derivative of such acid.

An important aspect of my invention pertains to the retarding of the development of rancidity of oils which tend to become rancid when exposed to air, and one of the chief objects of my invention, from this aspect, is to improve upon nitrocellulose dope compositions for use in coating of fabrics, paper, split leathers, and in general for leather substitute uses.

It has been customary for many years to use vegetable oils as softeners for pyroxylin compositions. For example, castor oil is very generally used in the surface film of artificial leather. and either castor oil or blown rapeseed oil is used in most of the dope applied to split leather. It is noteworthy that the oils used for this purpose belong for the most part in the class of unsaturated glycerides.

It is well known that unsaturated fatty oils, as, for example, castor oil, upon exposure to air, develop a rancid odor and taste which is quite objectionable. This rancidity development is especially marked where the oil is a. constiutent of a coating composition, for in this case, as a result of the extensive surface exposed to the air, the action of oxygen on the oil is facilitated.

The addition of various substances to oils for the purpose of preventing the development of rancidity therein was proposed many years ago; these substances comprised (a) halides, such as zinc chloride, (6) salts Renewed March 5, 1927.

of aromatic acids, for example sodium salicylate, (0) phenolates, such as sodium sulphocarbolate, and (d) naphthol. My experiments indicate that the preventive action of most of the above compounds is feeble; it is most pronounced in the case of betanaphthol, which, however, is hardly effective at all in preventing rancidity when the composition containing the oil is exposed to sunlight in the presence of air.

I have now discovered that oxalic acid and certain of its derivatives, such as sodium oxalate and ammonium oxalate are effective in retarding the development of rancidity in unsaturated substances such as unsaturated fatty oils.

The addition of even as small a quantity of one of the above substances as one part to one thousand parts of oil effects a marked decrease in the rate of rancidity development under conditions which are normally favorable to such a change.

The above discovery is particularly useful in preserving the freshness of the oil in coating compositions, where, for example, nitrocellulose, an oil, generally castor oil, and the rancidity-retarder are incorporated by means of a suitable volatile solvent and spread on a cloth backing. Upon aging, fabrics coated with the ordinary pyroxylin-oil composition often become sticky and finally brittle indicating deterioration of the coating composition. It has been found that oxalic acid compounds, that is, oxalic acid and oxalates, not only prevent rancidity development, but also greatly retard the deterioration to which such goods are liable. The rancidity-retarders thus are of great value in preserving the original pliable quality of the film.

The tests of the effects of the new rancidityretarders have been made in the following manner: To 100 parts of a nitrocellulose solution obtained by dissolving 16 ounces of nitrocellulose in one gallon of a mixture of ethyl acetate, benzol and ethyl alcohol, are

added 25 parts of castor oil, and 0.185 parts solvent to evaporate, the film obtained is TOO Clear fiZm 6'5 6'. storage Per cent retarder Rancid based on (days) oil Oxalic acid 7 0,75 12,15 Oxalic acid. .5 l 7 Sodium oxalate .5 10 Ammonium oxalate .5 T

The oxalic acid compounds, including oxalic acid and its salts and esters, which are within the scope of this invention may be described generically as compounds whose molecules contain the following atomic grouping:

Oxalic acid and its salts as distinguished from its esters may be referred to generically as compounds whose molecules contain the following atomic grouping:

where R represents a positive, reactive, inorganic radical, and particularly a hydrogen or an alkali-metal radical including the ammonium radical.

The eflicaey of the above-mentioned substaneesthat is, oxalic acid and the various oxalatesin functioning as oxidation-inhibitors depends largely upon the extensiveness of the surface of such substance which is in contact with the material to be conserved; that is. upon the extentto which intimate contact is attained between the inhibitor and said material. Intimate contact is most perfectly and conveniently attained when the inhibitor is soluble either in the unsaturated fatty oil which is to be conserved or in a liquid which is also a solvent for said oil. Where the inhibitor is not appreciably soluble in the oil, and where no suitable mutual solvent is available, it becomes necessary to disseminate the oxidation-inhibitor throughout the oil as thoroughly as possible, preferably by various known methods for effecting a high degree of dispersion. For the above reason there is in some cases an advantage in using the alkali-metal (including ammonium) salts of oxalic acid rather than themore insoluble oxalates or than the free acid I claim:

1. The process of retarding the development of rancidity in unsaturated fatty oils which comprises mixing with such an oil an oxalic acid compound whose molecules con tain the following atomic grouping:

grouping:

-0.0C.C0.0-R

where R represents a positive, reactive, in organic radical.

4. A composition of matter comprising av fatty material having a tendency to become rancid and an oxalic acid compound whose molecules contain the following atomic grouping:

0.0C.C0.0R

where R stanc s for the radical of a member of a group which includes hydrogen and the alkali-metals.

5. A composition of matter comprising a fatty material having a tendency to become rancid and an alkali-metal oxalate.

6. A composition of matter comprising an unsaturated vegetable oil and a compound whose molecule contains the following atomic grouping 0.0C.C0.0R

where R represents a positive, reactive, inorganic radical.

7. A composition of. matter comprising an unsaturated vegetable oil and from about 0.1% to 2.0%, based on the amount of oil present, of a. compound whose molecule contains the following atomic grouping:

8. A coating composition comprising nitrocellulose. a vegetable oil. and a compound whose molecule contains the following atomic grouping 0.0C.C0.0 R

where It stands for the radical of a member of a group which includes hydrogen and the alkali-metals.

9. A coating composition comprising nitro- 106. COMPOSITIONS,

COATING QR PLASTIC.

cellulose, a Vegetable oil, and an alkali-metal oxalate.

10. A coating composition comprising nitrocellulose, castor oil, and an oxalic acid compound whose molecules contain the fol lowing atomic grouping:

Where R and R each represents a radical of a member of a group which includes hydrogen and the alkali-metals.

11. A coating composition containing nitrocellulose, a softener for said nitrocellulose comprising a substance having a tendency to undergo oxidation when exposed to air, and a compound capable of inhibiting said oxidation whose molecule contains the following atomic grouping:

Where R stands for the radical of a member of a group which includes hydrogen and the alkali-metals.

12. A coating composition containing nitrocellulose, a softener for said nitrocellulose comprising a substance having a tendency to undergo oxidation when exposed to air, and from about 0.1% to 2.0%, based upon the amount of said substance, of a compound capable of inhibiting said oxidation whose molecule contains the following atomic grouping:

13. A coating composition comprising, in solution in a volatile solvent, nitrocellulose, an unsaturated oil, and an oxalic acid compound in an amount sufficient to practically prevent development of rancidity in said oil when the composition, in the form of a film,

is exposed to air at room temperature.

14. The process of retarding the development of rancidity in unsaturated fatty oils which comprises effecting a high degree of dispersion of a salt of oxalic acid throughout the oil.

15. The process of retarding the development of rancidity in unsaturated fatty oils which comprises effecting the dispersion of an oxidation inhibitor comprising a salt of oxalic acid which is soluble in unsaturated fatty oil.

16. A composition of matter comprising a fatty material having a tendency to become rancid, and, as a rancidity retarder, an organic substance comprising a salt of oxalic acid.

17. A film comprising a fatty material having a tendency to become rancid and, as a rancidity retarder, an organic substance comprising an alkaline metal salt of oxalic acid.

In testimony whereof I aflix my signature.

THOMAS HUNTON ROGERS. 

